// Copyright (c) 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/debug/proc_maps_linux.h"

#include <fcntl.h>
#include <stddef.h>

#include "base/files/file_util.h"
#include "base/files/scoped_file.h"
#include "base/strings/string_split.h"
#include "build/build_config.h"

#if defined(OS_LINUX) || defined(OS_ANDROID)
#include <inttypes.h>
#endif

#if defined(OS_ANDROID) && !defined(__LP64__)
// In 32-bit mode, Bionic's inttypes.h defines PRI/SCNxPTR as an
// unsigned long int, which is incompatible with Bionic's stdint.h
// defining uintptr_t as an unsigned int:
// https://code.google.com/p/android/issues/detail?id=57218
#undef SCNxPTR
#define SCNxPTR "x"
#endif

namespace base {
namespace debug {

    // Scans |proc_maps| starting from |pos| returning true if the gate VMA was
    // found, otherwise returns false.
    static bool ContainsGateVMA(std::string* proc_maps, size_t pos)
    {
#if defined(ARCH_CPU_ARM_FAMILY)
        // The gate VMA on ARM kernels is the interrupt vectors page.
        return proc_maps->find(" [vectors]\n", pos) != std::string::npos;
#elif defined(ARCH_CPU_X86_64)
        // The gate VMA on x86 64-bit kernels is the virtual system call page.
        return proc_maps->find(" [vsyscall]\n", pos) != std::string::npos;
#else
        // Otherwise assume there is no gate VMA in which case we shouldn't
        // get duplicate entires.
        return false;
#endif
    }

    bool ReadProcMaps(std::string* proc_maps)
    {
        // seq_file only writes out a page-sized amount on each call. Refer to header
        // file for details.
        const long kReadSize = sysconf(_SC_PAGESIZE);

        base::ScopedFD fd(HANDLE_EINTR(open("/proc/self/maps", O_RDONLY)));
        if (!fd.is_valid()) {
            DPLOG(ERROR) << "Couldn't open /proc/self/maps";
            return false;
        }
        proc_maps->clear();

        while (true) {
            // To avoid a copy, resize |proc_maps| so read() can write directly into it.
            // Compute |buffer| afterwards since resize() may reallocate.
            size_t pos = proc_maps->size();
            proc_maps->resize(pos + kReadSize);
            void* buffer = &(*proc_maps)[pos];

            ssize_t bytes_read = HANDLE_EINTR(read(fd.get(), buffer, kReadSize));
            if (bytes_read < 0) {
                DPLOG(ERROR) << "Couldn't read /proc/self/maps";
                proc_maps->clear();
                return false;
            }

            // ... and don't forget to trim off excess bytes.
            proc_maps->resize(pos + bytes_read);

            if (bytes_read == 0)
                break;

            // The gate VMA is handled as a special case after seq_file has finished
            // iterating through all entries in the virtual memory table.
            //
            // Unfortunately, if additional entries are added at this point in time
            // seq_file gets confused and the next call to read() will return duplicate
            // entries including the gate VMA again.
            //
            // Avoid this by searching for the gate VMA and breaking early.
            if (ContainsGateVMA(proc_maps, pos))
                break;
        }

        return true;
    }

    bool ParseProcMaps(const std::string& input,
        std::vector<MappedMemoryRegion>* regions_out)
    {
        CHECK(regions_out);
        std::vector<MappedMemoryRegion> regions;

        // This isn't async safe nor terribly efficient, but it doesn't need to be at
        // this point in time.
        std::vector<std::string> lines = SplitString(
            input, "\n", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);

        for (size_t i = 0; i < lines.size(); ++i) {
            // Due to splitting on '\n' the last line should be empty.
            if (i == lines.size() - 1) {
                if (!lines[i].empty()) {
                    DLOG(WARNING) << "Last line not empty";
                    return false;
                }
                break;
            }

            MappedMemoryRegion region;
            const char* line = lines[i].c_str();
            char permissions[5] = { '\0' }; // Ensure NUL-terminated string.
            uint8_t dev_major = 0;
            uint8_t dev_minor = 0;
            long inode = 0;
            int path_index = 0;

            // Sample format from man 5 proc:
            //
            // address           perms offset  dev   inode   pathname
            // 08048000-08056000 r-xp 00000000 03:0c 64593   /usr/sbin/gpm
            //
            // The final %n term captures the offset in the input string, which is used
            // to determine the path name. It *does not* increment the return value.
            // Refer to man 3 sscanf for details.
            if (sscanf(line, "%" SCNxPTR "-%" SCNxPTR " %4c %llx %hhx:%hhx %ld %n",
                    &region.start, &region.end, permissions, &region.offset,
                    &dev_major, &dev_minor, &inode, &path_index)
                < 7) {
                DPLOG(WARNING) << "sscanf failed for line: " << line;
                return false;
            }

            region.permissions = 0;

            if (permissions[0] == 'r')
                region.permissions |= MappedMemoryRegion::READ;
            else if (permissions[0] != '-')
                return false;

            if (permissions[1] == 'w')
                region.permissions |= MappedMemoryRegion::WRITE;
            else if (permissions[1] != '-')
                return false;

            if (permissions[2] == 'x')
                region.permissions |= MappedMemoryRegion::EXECUTE;
            else if (permissions[2] != '-')
                return false;

            if (permissions[3] == 'p')
                region.permissions |= MappedMemoryRegion::PRIVATE;
            else if (permissions[3] != 's' && permissions[3] != 'S') // Shared memory.
                return false;

            // Pushing then assigning saves us a string copy.
            regions.push_back(region);
            regions.back().path.assign(line + path_index);
        }

        regions_out->swap(regions);
        return true;
    }

} // namespace debug
} // namespace base
